Hi perl-diddler,

So why can't I add the global switch to the "qr" expression?

Here are some of my thoughts about the "why" part of the question: the way I like to think of this is that /g doesn't modify the regular expression (the inside of the /.../ construct), it modifies how m// and s/// work. A thorough reading of Regexp Quote Like Operators shows that this behavior is pretty complex, and for example the return values of m// depend on context, whether or not the regular expression contains capturing groups, and whether the /g modifier is present. Consider that when you construct a regular expression with qr//, it is not yet known what kind of regular expression operator it will be used in - it can be used in both an m// and an s///. Lastly, consider this hypothetical situation:

my $foo = qr/foo/g;     # hypothetical, won't work
my $bar = qr/bar(\d+)/;
while (<>) {
    while (/$foo$bar/) {...} # endless loop or not?
    my @x = /$foo$bar/;      # what's the return value?
    s/$bar$foo/quz$1/;       # replaces first or all matches?
    # ... etc. ...
}
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Hope this helps,
-- Hauke D