Re^2: Non-greedy substitution

Solution:
sub join_list { return "none" if !@_; # ??? my $last = pop; return $last if !@_; return join( ", ", @_ ) . " and " . $last; }
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An interesting solution.

However, in my quest to understand what is going on, I tried forcing the match to be non-comma characters and came up with this which produces the desired behaviour.

perl -e "my $test = join ', ', ('A', 'B', 'C');$test =~ s/,([^,]+?)$/ 
+and$1/; print $test;"
[download]

I still don't understand why the original doesn't work. Surely ,.+?$ is the shortest possible match within the string that starts with a comma and ends at the end of the line...

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Re^3: Non-greedy substitution by ikegami (Patriarch) on Nov 15, 2024 at 20:00 UTC
Your mental model of what «`.+?`» does is severely flawed. For starters, it doesn't permit patterns to have multiple subpatterns that can match substrings of different lengths. «`.+?`» does not mean "the shortest possible match within the string that starts with a comma". «`.+`» means "one or more non-LF characters, trying in order of decreasing length", and «`.+?`» means "one or more non-LF characters, trying in order of increasing length". Note that lack of mention of comma. «`.+?`» doesn't do any checks related to commas. The comma is matched independently.	[reply] [d/l] [select]
Re^4: Non-greedy substitution by Bod (Parson) on Nov 15, 2024 at 21:38 UTC
Your mental model of what Ť.+?ť does is severely flawed Well, yes...hence the need to ask the question... Ť.+?ť doesn't do any checks related to commas But I included the comma in my example...perhaps I could have formatted it so it was more prominent.	[reply]
Re^5: Non-greedy substitution by ikegami (Patriarch) on Nov 18, 2024 at 01:34 UTC
I know. But you said you thought Ť,.+?$ť searches for "the shortest possible match within the string that starts with a comma". Since neither «`,`» nor «`$`» searches for the shortest possible anything (starting with a comma or otherwise), that means you though «`.+?`» did that. «`.+?`» doesn't search for commas, which it would need to do to find "the shortest possible match within the string that starts with a comma".	[reply] [d/l] [select]