Hello all,

I'm developing a bundle for handling biomolecular structure files (PDB files). I'm now working on 

getting the language description sorted out. In doing this I ran into a regex problem.

The situation:

A PDB file is essentially a table. One line from such a table can be as follows:

ATOM     14  CA  GLN A   2     -27.648  -9.581  30.325  1.00 10.00

In the language description I would like to use a regular expression construct that 

matched 'GLN' only if the line starts with either 'ATOM' or 'HETATM'. This seams like

a conditional regular expression but my attempts to implement it at such have failed

so far.

Can anyone help?

Thanks,

Marc