Perl function to trim leading and trailing spaces from a string

Leading and trailing spaces, if any present, are trimmed and the string is returned back to the caller. If a NULL string is passed, the function does nothing.

 sub fstr_trim ($)
{
        # Arguments: The string to be trimmed.
        my ($mstr_original) = @_;
        #if a null/empty string is passed, just quit
        return unless(defined $mstr_original);

        $mstr_original =~ s/[s]+$//g;
        $mstr_original =~ s/^[s]+//g;
        $mstr_original =~ s/^ +//g;
        $mstr_original =~ s/ +$//g;
        return($mstr_original);
} # end of fstr_trim