Check out "perldoc Cwd" -- the Cwd module is part of the core distribution (everyone who has perl5 has this module):

use Cwd;

# ...

my $cwd = getcwd();

# ...
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Also, if you are confident that the config file is always installed in the same directory as the perl script, then you can check the vale of $0 (that's "dollar-sign, digit-zero"):

use File::Basename;  # another core module

# ...

my $script_path = ( fileparse( $0 ))[1];  # look for config file in $s
+cript_path

# (update: as peckingham points out, "dirname()" is easier)
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