my $var = qq{onChange="[document.approveform.command.value='approve'; document.approveform.submit();]" onClick="[if (this.disabled) {alert('some text!');}]"};

my ($onchange,$onclick);
if ($var =~ /onChange/) {
$var =~ /onChange\=\"\[(,*)\]\"/;
$onchange = $1;
}
if ($var =~ /onClick/) {
$var =~ /onClick\=\"\[(.*)\]\"/;
$onclick = $1;
}

Results:
 >> $onchange = whole $var exept the start >> onChange="[ <<
    and in the end >> ]" <<
 >> $onclick = just the onClick part, just as it should be.