Q: newbie wants to eval()

[lynx]

i want to iterate over a list of variable names, comparing each in turn
to a regexp match part, and if the comparison is equal, set the value of
the variable to the value given in another part of the same regexp
match; which seems most obviously done with eval().

i.e., i want to parse a configuration file of the rough form
variable_name = variable_value, and i want to make sure the variable
being set is on a list of variables i'm willing to allow setting, so i
don't want to just eval() the whole line - hence the list iteration.

trouble is, i've never used eval() for anything before, and i can't seem
to get the syntax right. given a loop iterator variable i, which 
iterates over a list of variable names, and a regexp match variable m,
which can be assumed to hold the value i'd like to assign to the named
variable, what should the eval expression look like, and why - how would
the bits and pieces of the complete, correct expression work together? i
ask because none of my current efforts work at all, and i can't figure
out why.

one little additional twist is that the variables i'm trying to set are
globals, defined outside the configuration-file-reading-function itself.
does this change some argument to the eval(), and if so, how?

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