I found the following method to be simple and readable in terms of configuration file syntax:

TOKEN1=value1
TOKEN2=value2
...
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The way to parse it is

while(<>) {
  if (/^([A-Z_]+)=(.*)/) {
     my ($TAG,$VAL)=($1,$2);
     $conf{$1}=$2;
  }
}
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This lets you have comment lines and can be easily extended for multi-line values, if needed.

Using __DATA__ section in your script is also useful, as mentioned by Corion, but you can just initialize %conf by

%conf=(TOKEN1 => "value1",
       TOKEN2 => "value2")
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Cheers.