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

my ($file1, $file2) = @ARGV;
my %hash_file1;
open my $FILE1, "<", $file1 or die "Cannot open $file1 for processing!\n";
while (my $line = <$FILE1>) {
    my ($key, @fields) = split /\s+/, $line;
    $hash_file1{$key} = join ":", @fields;
}
close $FILE1;
open my $FILE2, "<", $file2 or die "Cannot open $file2 for processing!\n";
while (my $line = <$FILE2>) {
    my ($key, @fields) = split /\s+/, $line;
    my $rest_of_line = join ":", @fields;
    if (exists $hash_file1{$key}) {         # this is a common record (same identifier)
        print $key, ":", $hash_file1{$key}, ":", $rest_of_line, "\n";
    }
} 
close $FILE2;