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Re^3: Why split function treats single quotes literals as regex, instead of a special case?

by jwkrahn (Monsignor)
on Aug 14, 2020 at 09:16 UTC ( #11120713=note: print w/replies, xml ) Need Help??


in reply to Re^2: Why split function treats single quotes literals as regex, instead of a special case?
in thread Why split function treats single quotes literals as regex, instead of a special case?

The regular expression // works differently in split then elsewhere:

$ perl -le' my $x = "1234 abcd 5678"; print $& if $x =~ /[a-z]+/; print $& if $x =~ //; print map qq[ "$_"], split /[a-z]+/, $x; print map qq[ "$_"], split //, $x; ' abcd abcd "1234 " " 5678" "1" "2" "3" "4" " " "a" "b" "c" "d" " " "5" "6" "7" "8"

Also, the line anchors /^/ and /$/ don't require the /m option to match lines in a string.

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Re^4: Why split function treats single quotes literals as regex, instead of a special case?
by AnomalousMonk (Bishop) on Aug 14, 2020 at 18:17 UTC
    The regular expression // works differently in split then elsewhere...

    I think I'd consider this just another special-case fixup prior to running split rather than a true difference in the function of m//:

    c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le "my $x = qq{1234 abcd 5678}; dd split //, $x; dd split /\b|\B/, $x; " (1 .. 4, " ", "a" .. "d", " ", 5 .. 8) (1 .. 4, " ", "a" .. "d", " ", 5 .. 8)
    This is probably just a matter of emphasis and interpretation.

    ... line anchors /^/ and /$/ don't require the /m option to match lines in a string.

    Checking the docs, I recalled seeing this discussed before, but it's another one of those very specialized special cases that evaporates from my memory with time. However, it's not true for the /$/ case (per the docs (or at any rate, the docs say nothing about special-casing it)):

    c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le "my $x = qq{1234 \n abcd \n 5678}; dd split /^/, $x; dd split /$/, $x; " ("1234 \n", " abcd \n", " 5678") "1234 \n abcd \n 5678"


    Give a man a fish:  <%-{-{-{-<

Re^4: Why split function treats single quotes literals as regex, instead of a special case?
by jcb (Vicar) on Aug 14, 2020 at 23:07 UTC
    The regular expression // works differently in split then elsewhere

    I think it is actually the other way around — in most contexts, m// is special (it refers to the most recent pattern without duplicating that pattern), while in split, // is literally the empty regex, which matches the zero-length empty string.

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