B::Showlex(3p) Perl Programmers Reference Guide B::Showlex(3p) #

B::Showlex(3p) Perl Programmers Reference Guide B::Showlex(3p)

NNAAMMEE #

 B::Showlex - Show lexical variables used in functions or files

SSYYNNOOPPSSIISS #

         perl -MO=Showlex[,-OPTIONS][,SUBROUTINE] foo.pl

DDEESSCCRRIIPPTTIIOONN #

 When a comma-separated list of subroutine names is given as options,
 Showlex prints the lexical variables used in those subroutines.
 Otherwise, it prints the file-scope lexicals in the file.

EEXXAAMMPPLLEESS #

 Traditional form:

  $ perl -MO=Showlex -e 'my ($i,$j,$k)=(1,"foo")'
  Pad of lexical names for comppadlist has 4 entries
  0: (0x8caea4) undef
  1: (0x9db0fb0) $i
  2: (0x9db0f38) $j
  3: (0x9db0f50) $k
  Pad of lexical values for comppadlist has 5 entries
  0: SPECIAL #1 &PL_sv_undef
  1: NULL (0x9da4234)
  2: NULL (0x9db0f2c)
  3: NULL (0x9db0f44)
  4: NULL (0x9da4264)
  -e syntax OK

 New-style form:

  $ perl -MO=Showlex,-newlex -e 'my ($i,$j,$k)=(1,"foo")'
  main Pad has 4 entries
  0: (0x8caea4) undef
  1: (0xa0c4fb8) "$i" = NULL (0xa0b8234)
  2: (0xa0c4f40) "$j" = NULL (0xa0c4f34)
  3: (0xa0c4f58) "$k" = NULL (0xa0c4f4c)
  -e syntax OK

 New form, no specials, outside O framework:

  $ perl -MB::Showlex -e \
     'my ($i,$j,$k)=(1,"foo"); B::Showlex::compile(-newlex,-nosp)->()'
  main Pad has 4 entries
  1: (0x998ffb0) "$i" = IV (0x9983234) 1
  2: (0x998ff68) "$j" = PV (0x998ff5c) "foo"
  3: (0x998ff80) "$k" = NULL (0x998ff74)

 Note that this example shows the values of the lexicals, whereas the
 other examples did not (as they're compile-time only).

OOPPTTIIOONNSS #

 The "-newlex" option produces a more readable "name => value" format, and
 is shown in the second example above.

 The "-nosp" option eliminates reporting of SPECIALs, such as "0: SPECIAL
 #1 &PL_sv_undef" above.  Reporting of SPECIALs can sometimes overwhelm
 your declared lexicals.

SSEEEE AALLSSOO #

 B::Showlex can also be used outside of the O framework, as in the third
 example.  See B::Concise for a fuller explanation of reasons.

TTOODDOO #

 Some of the reported info, such as hex addresses, is not particularly
 valuable.  Other information would be more useful for the typical
 programmer, such as line-numbers, pad-slot reuses, etc..  Given this,
 -newlex is not a particularly good flag-name.

AAUUTTHHOORR #

 Malcolm Beattie, "mbeattie@sable.ox.ac.uk"

perl v5.36.3 2017-02-05 B::Showlex(3p)