Hi all! I need to check if file indicated in the command line contains any symbols other than a, c, t or g. Here is what I wrote: 

 
#!/usr/bin/perl -w

use strict;

my $DNA;  
chomp ( $DNA = $ARGV[0] );
open ( INPUT_FILE, "$DNA" ) or die;
         
if ( <INPUT_FILE> =~ m/[^actgACTG]/ ) {
    print "File contains something besides actg sequence.\n";
} else {     
    print "good!\n";
}

[download]

The problem is that this code matches non actg symbols in files that contain only actg letters. Help please!

In reply to =~ matches non-existent symbols by Anonymous Monk

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