$ perl mygrep.pl refFlat.txt
Can't locate IO/FILE.pm in @INC (@INC contains: -->$<--/usr/lib/perl/5.10.1 /etc/perl /usr/local/lib/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl .) at mygrep.pl line 4.