This is assuming that you are looking for an exact match on the entire line. If not, then you can get rid of the leading ^ and $ .

#!/usr/local/bin/perl
use strict;
      
my $file = 'thesaurus';       # Name the file
# get this into an array unless the file is too big
open(INFO,$file) || die "Cannot open file"; 
my @lines = <INFO>;
close(INFO);            
print " what are you looking for? ";
$a = <STDIN>;
chomp $a;
my $found = 0;
foreach(@lines){ 
# get the match                                            
  if($found == 0){
    chomp;
    if(/^$a$/){$found = 1;}
  }
# print the next line
  else{
    print;
  } 
}
[download]

Hope this helps....

Mick