Thanks both---I didn't realise that $' was treated like that. Are all 'special variables' ($&, $N (N is integer)) expanded in that way too? So if you did something like:

$temp =~ m/(\[0-9\])blah$1/;
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would you match

$temp = "[0-9]blah6";
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rather than

$temp = "[0-9]blah[0-9]";
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?
V. interesting---I assumed that special characters inside the rest of the data would be ignored..
Cheers
<--edit to make the last sentence make more sense!-->