Do you mean something like this?

if( $text =~ /$query/i ) {
    while ( $text =~ /$query/gi ) {
        do_something();
    }
}
elsif( $text =~ /$query_modified/i ) {
    while ( $text =~ /$query_modified/gi ) {
        do_something_different();
    }
}
else {
    ## Is this possible?
}
[download]

Or perhaps:

while ( $text =~ /($query|$query_modified)/gi ) {
    if( $1 eq $query ) {
        do_something();
    }
    else {
        do_something_else();
    }
}
[download]