#! /usr/bin/env perl

use strict;
use warnings;

my %templates = (
    url => 'http://something.com/api_stuff/%guid%'
);

print format_template( url => guid => 1234 );

sub format_template {
    my $template_id = shift;

    my $template = $templates{$template_id};
    my (%args) = @_;

    foreach (keys %args) {
        $template =~ s/%$_%/$args{$_}/;
    }

    return $template;
}