You've tripped over the most-voodoo of Perl's parsing. $\ is a variable and the regex parser needs to decide whether $\n meant "end-of-line then newline" or "the contents of $\ then the letter 'n'". Perl prefers the latter interpretation. Several ways to try to resolve this don't work: 

perl -le'$_="ABC\nDEF"; s/C\$\n^D/-/m; print'
perl -le'$_="ABC\nDEF"; s/C$[\n]^D/-/m; print'

[download]

But there are several ways to successfully work around the problem: 

perl -le'$_="ABC\nDEF"; s/C$ \n^D/-/mx; print'
perl -le'$_="ABC\nDEF"; s/C(?:$)\n^D/-/m; print'
perl -le'$_="ABC\nDEF"; s/C$(?:\n)^D/-/m; print'

[download]

But they produce "AB-EF" not "ABC-DEF". And the following one will never match anything if it were parsed the way you expected, since there has to be a \n in the matched string between $ and ^: 

perl -le'$_="ABC\nDEF"; s/C$^D/-/m; print'

[download]

- tye        

In reply to Re: Why \n matches but not $^? (weight) by tye
in thread Why \n matches but not $^? by tel2

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