Re^2: transliterate a sub-string


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Re^2: transliterate a sub-string

by grondilu (Friar)

on Jan 16, 2013 at 07:18 UTC ( [id://1013516]=note: print w/replies, xml )

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in reply to Re: transliterate a sub-string
in thread transliterate a sub-string

This is neat, but was certainly not obvious. Maybe it is worth reminding that indeed substr can be used as a lvalue, as explicitely said in its perldoc:

You can use the substr() function as an lvalue, in which case EXPR must itself be an lvalue. If you assign something shorter than LENGTH, the string will shrink, and if you assign something longer than LENGTH, the string will grow to accommodate it. To keep the string the same length, you may need to pad or chop your value using "sprintf".

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Re^3: transliterate a sub-string
by Anonymous Monk on Jan 16, 2013 at 09:05 UTC

as explicitely said in its perldoc:

Said and shown :)

my $name = 'fred';
substr($name, 4) = 'dy';         # $name is now 'freddy'
my $null = substr $name, 6, 2;   # returns "" (no warning)
my $oops = substr $name, 7;      # returns undef, with warning
substr($name, 7) = 'gap';        # raises an exception
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Note that the lvalue returned by the three-argument version of substr() acts as a 'magic bullet'; each time it is assigned to, it remembers which part of the original string is being modified; for example:
$x = '1234';
for (substr($x,1,2)) {
    $_ = 'a';   print $x,"\n";    # prints 1a4
    $_ = 'xyz'; print $x,"\n";    # prints 1xyz4
    $x = '56789';
    $_ = 'pq';  print $x,"\n";    # prints 5pq9
}
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Wow, I can copy/paste :)

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