# sicherheitskopie
use File::Copy;
File::Copy::copy( $file, "$file.bak" )
  or die "Error: couldn't copy '$file': $!\n";

# datei ueberschreiben
open( my $OUTFILE, '>', $file )
  or die "Error: couldn't write to file '$file': $!\n";
print $OUTFILE @irgendwas
    or die "Error at printing to file '$file: $!\n";
close $OUTFILE
    or die "Error: couldn't close file '$file': $!\n";

# backup wegwerfen
unlink( "$file.bak" )
  or die "Error: couldn't unlink file '$file.bak': $!\n";