Re: matching and mysterious captures

If you modify your code to

echo -e 'zero\none\ntwo\n\n three' | perl -0777 -pe 's{\s*(one\ntwo)\s*?( *)}{\n\n<begin block>\n\n$1\n\n<end block>\n\nx$2x}'

so you have a clear delimiter around your second match, your get:

zero

<begin block>

one
two

<end block>

xx

    three
[download]

By swapping your space matching to non-greedy, you are no longer consuming the newlines preceding 'three'. You can get your expected result by using the multiline modifier (see Modifiers in perlre) combined with a line start metacharacter ^;

echo -e 'zero\none\ntwo\n\n three' | perl -0777 -pe 's{\s*(one\ntwo)\s*^( *)}{\n\n<begin block>\n\n$1\n\n<end block>\n\n$2}m'

yields

zero

<begin block>

one
two

<end block>

    three
[download]

Comment on Re: matching and mysterious captures Select or Download Code

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Re^2: matching and mysterious captures by Allasso (Monk) on May 05, 2011 at 17:15 UTC
I see, I was matching the minimum which was 0 \s's and 0 spaces. Your example works, except in the case of: `echo -e 'zero\none\ntwo three' \| perl -0777 -pe 's{\s(one\ntwo)\s +^( *)}{\n\n<begin block>\n\n$1\n\n<end block>\n\n$2}m' zero one two three` [download]	[reply] [d/l]
Re^3: matching and mysterious captures by kennethk (Abbot) on May 05, 2011 at 18:00 UTC
What do you expect to get for the case you've listed? This falls outside any of the cases you've described above - see I know what I mean. Why don't you?. If you expect to get `zero <begin block> one two <end block> three` [download] which cleans out blank lines but keeps the spaces before three, you can use a non-capturing group `(?:...)` combined with the `?` quantifier to make the whitespace matching conditional: `echo -e 'zero\none\ntwo three' \| perl -0777 -wpe 's{\s(one\ntwo)(?:\s^)?( *)}{\n\n<begin block>\n\n$1\n\n<end block>\n\n$2}m'`	[reply] [d/l] [select]
Re^4: matching and mysterious captures by Allasso (Monk) on May 05, 2011 at 18:51 UTC
ah yes, that's what I was looking for. I knew something like that would work, but I couldn't quite get the right combination. Sorry for the confusion, no, I didn't state my needs very clearly.	[reply]