The Devel namespace has lots of modules you can use for this sort of thing. You can, however, get some information on your own from the symbol table. Here is a simple illustration of that sort of thing from the command line,

$ perl -e'BEGIN{@ns{keys %::} = ()}; $foo = "bar";@names = grep {!exis
+ts $ns{$_}} keys %::; print "@names",$/'
foo names
$
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The BEGIN block collects all the keys of %main:: which exist before other stashes are formed and uses them as keys in the %ns hash. That hash is used to eliminate the 'noise' leaving only the names you have defined since.

That could be carried further by checking names against properties by the likes of,

print "foo has: ", $_, $"
        for (grep {*foo{$_} qw/SCALAR ARRAY HASH CODE GLOB IO/;
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The values may be examined by dereferencing. Again the command line,

$ perl -e'BEGIN{@ns{keys %::} = ()}; $foo = "bar";@names = grep {!exis
+ts $ns{$_}} keys %::; print ${*foo{SCALAR}} ,$/'
bar
$
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All this only addresses the symbol tables. Lexical variables are not accessible by this method.