We don't do homework assignments here.

Having said that, maybe you want to show us the code you already have, and explain to us what it should do, what its input data is, what it should ouput and how it fails for you? Then we can help you with your specific problems.

Alternatively, I'd just use Template Toolkit to fill out templates, but you'd have to rewrite your templates to fit in the TT syntax.

This is only a trace you can follow:

• read the second file, parsing each line (split) and populating a hash with var=>value
• open a temp file in write mode (File::Temp)
• read the first file and, line by line:
• extract the left term with a regex
• use it as a key to the hash
• retrieve the value
• substitute it in the line with another regex
• write the new line to a temp file
• on end of file, close the files and copy the temp file back in place of the first file (File::Copy)

Post the script you have written so far and explain exactly where you are stuck. Then you'll probably get much more concrete help.

This is UNTESTED but it may help get you started:

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

my $file2 = 'File2';

open my $IN, '<', $file2 or die "Cannot open '$file2' $!";

my %data;
while ( <$IN> ) {
    next unless /^([^=]+)=(.+)/;
    $data{ $1 } = $2;
    }

close $IN;

( $^I, @ARGV ) = ( '.bak', 'File1' );

while ( <> ) {
    s/(\@([^\@]+)\@)$/ exists $data{ $2 } ? $data{ $2 } : $1 /e;
    print;
    }
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