use warnings;
use strict;

my $filename = "000776654103_01_QY_20099976_776520.txt";
my $account = "7766541";

if ($filename =~/$account/) {
 print $filename."\n";
}else{
  print "No match for $account\n";
}

__END__

000776654103_01_QY_20099976_776520.txt