Re: Using regex in Map function

You need to remember that the result of map is the list of the final value of each pass through its block. The value of s/// is a boolean indicating whether a replacement was made. You want the final value of the map block to be $_. Like so:

@new = map { s/$_/$_,hi/; $_ } <TEST>;
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However, your substitution is less than ideal. In particular, you'll have problems if $_ contains any regex-special characters. If you're simply appending, you could do this:

@new = map { s/$/,hi/; $_ } <TEST>;
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or, even ~~better~~worse, this:

@new = map { $_ . ',hi' } <TEST>;
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A word spoken in Mind will reach its own level, in the objective world, by its own weight

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Re^2: Using regex in Map function by grinder (Bishop) on May 02, 2007 at 22:00 UTC
The value of s/// is a boolean indicating whether a replacement was made. Err, no, not really. It's actually the number of replacements made. Thus: `# given $x = 'abacad'; # then $x =~ s/a/z/; # returns 1 $x =~ s/a/z/g; # returns 3 $x =~ s/x/z/; # returns empty string, not undef` [download] ... although it can be treated quite nicely in a boolean manner :) • another intruder with the mooring in the heart of the Perl	[reply] [d/l]
Re^2: Using regex in Map function by jettero (Monsignor) on May 02, 2007 at 21:14 UTC
In addition to what jdporter is saying, I'd like to add that this is probably faster and clearer: `@new = <TEST>; s/something/something/ for @new;` [download] I haven't Benchmarked it or anything, but I'm pretty sure it's faster than `map {s/regex/stuff/}` — either way, it's probably more readable. -Paul	[reply] [d/l] [select]
Re^2: Using regex in Map function by pKai (Priest) on May 02, 2007 at 21:21 UTC
or, even better, this That may be subject to judgement. While your 1st and 3rd variant append behind the line-ending newline, the 2nd is probably closer to what the OP wanted, since `$` is matching before that newline.	[reply] [d/l]
Re^2: Using regex in Map function by strat (Canon) on May 03, 2007 at 09:57 UTC
If you need something like the copy - do something more often, you could also create a copy-wrapper for map, let's call it cwmap: `sub cwmap( &@ ) { map { local $_ = $_; # create copy $_[0]->(); # execute code-block $_; # copied element } @_[ 1..$#_ ]; # list } # cwmap # and then use it like map: @new = cwmap { s/$_/$_,hi/ } <TEST>;` [download] Best regards, perl -e "s>>F>e=>y)\martinF)stronat)=>print,print v8.8.8.32.11.32"	[reply] [d/l]