# http://avisynth.org/mediawiki/HDColorBars
Function StrReplace(string base, string sought, string rep)
    {
        pos = FindStr(base, sought)
        return (sought == "") || (pos == 0) \
            ? base \
            : StrReplace( \
                LeftStr(base, pos - 1) + rep + \
                MidStr(base, pos + StrLen(sought)), \
                sought, rep)
    }

# http://forum.doom9.org/showthread.php?t=102929
function ForNext(var_string, from_indx, to_indx, by_value, loop_string, format_string)
{
    result = ""
    LineBreak = """
"""
    from_indx <= to_indx ? Eval( "result = result + LineBreak + StrReplace(loop_string, var_string, String(from_indx, format_string))") : NOP
    (from_indx+by_value) <= to_indx ? Eval( "result = result + ForNext(var_string, (from_indx+by_value), to_indx, by_value, loop_string, format_string)") : NOP
    return result
}


# this example splices the following clips:
# cv3.avi
# cv3_part002.avi
# cv3_part003.avi
# cv3_part004.avi

a = AviSource ("cv3.avi")

Eval(ForNext ("${i}", 2, 4, 1, """a = a + AviSource ("cv3_part${i}.avi")""", "%03.0f"))

a