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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: SPECIAL #1 &PL_sv_undef 1: PVNV (0x9db0fb0) $i 2: PVNV (0x9db0f38) $j 3: PVNV (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,$k)=(1,"foo")' main Pad has 4 entries 0: SPECIAL #1 &PL_sv_undef 1: PVNV (0xa0c4fb8) "$i" = NULL (0xa0b8234) 2: PVNV (0xa0c4f40) "$j" = NULL (0xa0c4f34) 3: PVNV (0xa0c4f58) "$k" = NULL (0xa0c4f4c) -e syntax OK
New form, no specials, outside O framework:
$ perl -MB::Showlex -e \
'my ($i,$j,$k)=(1,"foo"); B::Showlex::compile(-newlex,-nosp)->()'
main Pad has 4 entries
1: PVNV (0x998ffb0) "$i" = IV (0x9983234) 1
2: PVNV (0x998ff68) "$j" = PV (0x998ff5c) "foo"
3: PVNV (0x998ff80) "$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 isnt a particularly good flag-name.
Malcolm Beattie, mbeattie@sable.ox.ac.uk