Perl: Use s/ (replace) and return new string [dupl

问题:

This question already has answers here:

How do I perform a Perl substitution on a string while keeping the original? (7 answers)

Closed 5 months ago.

In Perl, the operator s/ is used to replace parts of a string. Now s/ will alter its parameter (the string) in place. I would however like to replace parts of a string befor printing it, as in

print "bla: ", replace("a","b",$myvar),"\n";

Is there such replace function in Perl, or some other way to do it? s/ will not work directly in this case, and I'd like to avoid using a helper variable. Is there some way to do this in-line?

回答1:

Untested:

require 5.013002;
print "bla: ", $myvar =~ s/a/b/r, "\n";

See perl5132delta:

The substitution operator now supports a /r option that copies the input variable, carries out the substitution on the copy and returns the result. The original remains unmodified.

my $old = 'cat';
my $new = $old =~ s/cat/dog/r;
# $old is 'cat' and $new is 'dog'

回答2:

If you have Perl 5.14 or greater, you can use the /r option with the substitution operator to perform non-destructive substitution:

print "bla: ", $myvar =~ s/a/b/r, "\n";

In earlier versions you can achieve the same using a do() block with a temporary lexical variable, e.g.:

print "bla: ", do { (my $tmp = $myvar) =~ s/a/b/; $tmp }, "\n";

回答3:

print "bla: ", $myvar =~ tr{a}{b},"\n";

回答4:

print "bla: ", $_, "\n" if ($_ = $myvar) =~ s/a/b/g or 1;

回答5:

If you really want, you can make your own, but I wouldn't because you have much more functionality with s/// ... you could build that functionality into your function, but why recreate something that already exists?

#!/usr/bin/perl -w    

use strict;     

   main();   

   sub main{    
      my $foo = "blahblahblah";          
      print '$foo: ' , replace("lah","ar",$foo) , "\n";  #$foo: barbarbar

   }        

   sub replace {
      my ($from,$to,$string) = @_;
      $string =~s/$from/$to/ig;                          #case-insensitive/global (all occurrences)

      return $string;
   }