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To work on $_ by default, check the size of @_. For example,
sub func { local $_ =   @_ ? $_[0] : $_;  ... } # copy
sub func { local *_ = \(@_ ? $_[0] : $_); ... } # alias

To request a scalar argument, use prototypes. For example,
sub func($)  { ... } # scalar
sub func(;$) { ... } # optional scalar
This is required for $str = my_uc my_reverse 'ab', 'cd'; to work.

Finally, use wantarray to determine whether a list or a scalar (or nothing at all) should be returned.

In Perl, your functions would be the following:

sub pp_lcfirst(;$) { local $_ = @_ ? $_[0] : $_; s/(.)/\l$1/; return $_; } sub pp_uc(;$) { local $_ = @_ ? $_[0] : $_; s/(.*)/\U$1/; return $_; } sub pp_reverse { if (wantarray) { my @rv; push(@rv, pop(@_)) while @_; return @rv; } else { my $str = join('', @_); my $rv = ''; my $i = length($str); $rv .= substr($str, $i, 1) while $i--; return $rv; } } sub spaces_to_und(;$) { local $_ = @_ ? $_[0] : $_; s/\s+/_/g; return $_; }

Update: Cleanup.

Update: Fixed the typo japhy noticed in my prototypes.

In reply to Re: subroutine bewilderment: how to mimic builtins by ikegami
in thread subroutine bewilderment: how to mimic builtins by dimar

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    [hippo]: How did you install libapreq2?
    [vedagiri89]: that one is done by system team from the tar i guess
    [hippo]: Really? Not using the one from the CentOS repository? Perhaps that's the problem.
    [vedagiri89]: i need when this issue will come usually
    [hippo]: How about mod_perl? Was that installed from the CentOS packge or from source?
    [vedagiri89]: from the source
    [hippo]: But is under vendor_perl in your error message so you are mixing up modules installed from the packager and by hand. That's rarely a good plan.
    [vedagiri89]: the prm fine if i run file directly..not working if i run through apache http file
    [hippo]: Environments differ.
    [vedagiri89]: so, how to fix that differ

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