Question

    $rowfetch =~ s/['-]//g; #All chars inside the [ ] will be filtered out.     $rowfetch =~ m/(\w+), ?(.)/;     printf $fh lc($2.$1); 

I got help building this regular expression yesterday, but I don’t fully understand it.

It takes a name like Parisi, Kenneth and prints out kparisi

Knowns:
s/ = substitute
m/ = match

I tried searching for the rest but couldn’t find anything that really helped explain it.

I also didn’t understand how the =~ is supposed to evaluate to either true or false, yet in this situation, it is modifying the string.

Answer 1

I keep one of these cheat sheets pinned on my cube wall for just such occasions. Google for regular expression cheat sheet to find others.

To add to what you already know:

  g -- search globally throughout the string   + -- match at least one, but as many as possible   ? -- match 0 or 1   . -- match any character  () -- group these together   , -- a plain comma, no special meaning  [] -- match any character inside the brackets  \w -- match any word character 

The magic is in the grouping — the match expression uses the groups and puts them into variables $1 and $2. In this case $1 matches the word before the comma and $2 matches the first character following the whitespace after the comma.