This really has me puzzled. Say I have a files that may have the occurance of "one\ntwo" within:

echo -e 'zero\none\ntwo\n\n    three'
zero
one
two

    three

[download]

I want to recurse through the files, and if they contain the block "one\ntwo", I want to put identifiers around it, and a prescribed number of newlines, regardless of how many there were before:

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}'
zero

<begin block>

one
two

<end block>

three

[download]

Great - but I want to preserve the offset of the first word on the rest of the text that follows. So I think, no problem, I'll just do this:

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}'
zero

<begin block>

one
two

<end block>



    three

[download]

It preserves the indent, but now I have additional newlines after <end block>. Where did they come from? The second capture is only capturing spaces, so how did two extra \n's get inserted?

In reply to matching and mysterious captures by Allasso

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