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#!/usr/bin/perl -w use strict; $\="\n"; ## first, to BrowserUk's misunderstanding, an explanation my $s = 'ABCD'; print substr($s,0,2)=''; # EXPECT 'CD', what's left print $s; # CD $s = 'ABCD'; print substr($s,0,2,''); # EXPECT 'AB', print $s; # CD # perldoc -f substr # An alternative to using substr() as an lvalue is to specify the # replacement string as the 4th argument. This allows you to # replace parts of the EXPR and return what was there before in # one operation, just as you can with splice(). my @B = 1..4; print splice(@B,0,2,()); # expect 12 print @B; # expect 34 # perldoc -f splice # Removes the elements designated by OFFSET and LENGTH from an # array, and replaces them with the elements of LIST, if any. In # list context, returns the elements removed from the array. # now to tye's argument, saying that substr($s,0,2)= EXPR # doesn't return EXPR and is therefore a bug # perldoc -f substr # You can use the substr() function as an lvalue, in which case # EXPR must itself be an lvalue. $s = '1234'; @B=(); $B[0] = substr($s,0,2) = 'ab'; print $s; # EXPECT ab34 print "@B"; # EXPECT ab print "ASSIGN '' "; $s = '1234'; @B=(); $B[0] = substr($s,0,2) = ''; print $s; # expect 34 print "@B"; # EXPECT 34, cause '' wouldn't be an lvalue print "ASSIGN undef "; $s = '1234'; @B=(); $B[0] = substr($s,0,2) = undef; print $s; # expect 34 print "@B"; # EXPECT 34, cause undef wouldn't be an lvalue ## CONCLUSION ## if '' and undef are lvalues, then this is a feature, and not a bug __END__ CD CD AB CD 12 34 ab34 ab ASSIGN '' 34 34 ASSIGN undef Use of uninitialized value in scalar assignment at BrowserUk.substr.pl + line 51. 34 34

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In reply to Re: [substr] anomaly or mine? by PodMaster
in thread [substr] anomaly or mine? by BrowserUk

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