"my" variable $test masks earlier declaration in same scope at test_verschluesselung.pl line 75 (#1) (W misc) A "my", "our" or "state" variable has been redeclared in the current scope or statement, effectively eliminating all access to the previous instance. This is almost always a typographical error. Note that the earlier variable will still exist until the end of the scope or until all closure referents to it are destroyed. Integer overflow in hexadecimal number at test_verschluesselung.pl line 447 (#2) (W overflow) The hexadecimal, octal or binary number you have specified either as a literal or as an argument to hex() or oct() is too big for your architecture, and has been converted to a floating point number. On a 32-bit architecture the largest hexadecimal, octal or binary number representable without overflow is 0xFFFFFFFF, 037777777777, or 0b11111111111111111111111111111111 respectively. Note that Perl transparently promotes all numbers to a floating point representation internally--subject to loss of precision errors in subsequent operations. Hexadecimal number > 0xffffffff non-portable at test_verschluesselung.pl line 447 (#3) (W portable) The hexadecimal number you specified is larger than 2**32-1 (4294967295) and therefore non-portable between systems. See perlport for more on portability concerns. Integer overflow in hexadecimal number at test_verschluesselung.pl line 559 (#2) Hexadecimal number > 0xffffffff non-portable at test_verschluesselung.pl line 559 (#3) Global symbol "@W" requires explicit package name at test_verschluesselung.pl line 93. Global symbol "@keyback" requires explicit package name at test_verschluesselung.pl line 410. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 411. Global symbol "@keyback" requires explicit package name at test_verschluesselung.pl line 411. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "@key" requires explicit package name at test_verschluesselung.pl line 413. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 413. Global symbol "$ctrTxt" requires explicit package name at test_verschluesselung.pl line 418. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "$ctrTxt" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "@key" requires explicit package name at test_verschluesselung.pl line 426. Global symbol "$cipherCntr" requires explicit package name at test_verschluesselung.pl line 449. Global symbol "$cipherCntr" requires explicit package name at test_verschluesselung.pl line 456. Global symbol "$plaintext" requires explicit package name at test_verschluesselung.pl line 467. Global symbol "$plaintext" requires explicit package name at test_verschluesselung.pl line 468. Global symbol "$keyexp" requires explicit package name at test_verschluesselung.pl line 516. Global symbol "$keyexp" requires explicit package name at test_verschluesselung.pl line 520. Execution of test_verschluesselung.pl aborted due to compilation errors (#4) (F) You've said "use strict" or "use strict vars", which indicates that all variables must either be lexically scoped (using "my" or "state"), declared beforehand using "our", or explicitly qualified to say which package the global variable is in (using "::"). Uncaught exception from user code: Global symbol "@W" requires explicit package name at test_verschluesselung.pl line 93. Global symbol "@keyback" requires explicit package name at test_verschluesselung.pl line 410. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 411. Global symbol "@keyback" requires explicit package name at test_verschluesselung.pl line 411. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 412. Global symbol "@key" requires explicit package name at test_verschluesselung.pl line 413. Global symbol "$key" requires explicit package name at test_verschluesselung.pl line 413. Global symbol "$ctrTxt" requires explicit package name at test_verschluesselung.pl line 418. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 419. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "$ctrTxt" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "$i" requires explicit package name at test_verschluesselung.pl line 420. Global symbol "@key" requires explicit package name at test_verschluesselung.pl line 426. Global symbol "$cipherCntr" requires explicit package name at test_verschluesselung.pl line 449. Global symbol "$cipherCntr" requires explicit package name at test_verschluesselung.pl line 456. Global symbol "$plaintext" requires explicit package name at test_verschluesselung.pl line 467. Global symbol "$plaintext" requires explicit package name at test_verschluesselung.pl line 468. Global symbol "$keyexp" requires explicit package name at test_verschluesselung.pl line 516. Global symbol "$keyexp" requires explicit package name at test_verschluesselung.pl line 520. Execution of test_verschluesselung.pl aborted due to compilation errors.