System execute

1. using `` symbol
2. using system function

Case 1: grep need the escape in search
{{{
#!/usr/bin/perl

use strict;
use warnings;

my $r = `grep "\\w" FGSH_TIR.gff.GOA.overlap.entries.Annotation_2`;
#my $r = `echo hello`;
print $r;


system ("cat FGSH_TIR.gff.GOA.overlap.entries.Annotation_2 | grep"."\'\\w\'"."> tt");

}}}