B::Showlex - Show lexical variables used in functions or files
- perl -MO=Showlex[,-OPTIONS][,SUBROUTINE] foo.pl
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.
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).
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.
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.
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.
Malcolm Beattie, mbeattie@sable.ox.ac.uk