On a related note: Any ideas why this: 
    while( substr( $$str, $y * $WIDTH, $WIDTH ) =~ m[((.)\2*)]mg ) {
    ...

[download]
Works (runs to completion, produces the desired results) on 5.10.1, but silently loops forever in 5.22.0?
Looks like a bug fix. expr =~ /.../g attaches position magic to the LHS after each match, to record the current pos() for that expression. If expr is a var or similar this works well; if expr returns something new each time, the old pos magic gets lost.

This similarly loops forever: 

sub f { "abc" }

1 while f() =~ /./g;

[download]

Dave.

In reply to Re^3: Faster regex to split a string into runs of similar characters? by dave_the_m
in thread Faster regex to split a string into runs of similar characters? by BrowserUk

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