#!/usr/bin/perl

use strict;
use warnings;

print button(type => 'image', name => 'name', value=> 'test', text => 'Hallo');

sub button{
    my %args = @_;
    my $options = ' ';
    for my $key( qw(type name value) ){
        $options .= $key . '="' . $args{$key} . '"' if exists $args{$key};
    }
    my $text = $args{text} || 'defaulttext';
    print "<button $options>$text</button>";
}