#!/usr/bin/perl
use strict;
use warnings;

my $file = $ARGV[0] or die "Usage: $0 <input_file>";
open(my $fh, '<', $file) or die "Unable to open '$file' for reading: $!";

my $header = <$file>;
chomp $header;
my @field = split /:/, $header;

print "What field would you like to look for?\n";
my $choice = <STDIN>;
chomp $choice;

while (<$fh>) {
    chomp;
    my %record;
    @record{@field} = split /:/;
    print "$record{$choice}\n";
}