in reply to Re: Re: Substitution Problem
in thread Substitution Problem

Don't confuse matching with capturing:

s/$a/$b/     # $a matches and is replaced by $b
s/($a)/$1$b/ # $a matches and is captured in $1
             #   $b is appended

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Note also, that you can't use character classes like "." or "\s" within the right side of the substitute operator.

~Django
"Why don't we ever challenge the spherical earth theory?"

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Re: Re: Re: Re: Substitution Problem
by Wassercrats (Initiate) on Sep 13, 2002 at 02:42 UTC
    It crossed my mind that maybe I can't use character classes on the right side. I guess that was my only problem, but I think that should be allowed. If want delete all attributes from an anchor tag that's contained in @links1, except for href, it would be nice if the following (from my original message) would work:
    @links1=~s/.*/href\s*\=\s*\".*?\"/is;

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    with a slight adjustment if I want the angle brackets.
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[d/l]

      That wouldn't make much sense, because a character class can match any of its characters, but how should it be interpreted in the right side of s///? Should that mean all the characters it represents? Or a random one?
      The following code does what you want:

      for (@links1) {
  s/<\s*a\s.*?\b(href\s*=\s*".*?").*?>/<a $1>/i;
}

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      Now let me explain your errors:
      @links1=~   # that would work like scalar(@array)=~
s/ .*       # replace complete string with
 / href     # 'href'
   \s*      # as many spacey chars as possible
   \=       # no need to escape '='
   \s*      # as many spacey chars as possible
   \"       # no need to escape '"'
   .*?      # as few as possible (=no) anythings
   \"       # no need to escape '"'
 /isx;      # 's' is not needed, I added 'x'

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      ~Django
      "Why don't we ever challenge the spherical earth theory?"

[reply]
[d/l]
[select]
        I'm a beginner in Perl, but I think your breakdown of my code explains exactly what I want it to do. I went a little crazy with the escapes though. I'll need the s modifer for some other cases, though it's unnecessary for this example. I'd like the special meanings of the escaped characters on the right of the s/// to be used. I want the element in which the substitution is taking place (@links1[whatever]) to be referred to when Perl is assiging real text to the special characters. Not that you're solution is worse than my proposed one, but I was suprised to learn that mine didn't work.
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[d/l]

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