Need advice on pattern matching using match()

[Michael Klier]

Hi everybody,

I have a little problem with pattern matching using Vims' match()
function. I`ve wrote a syntax highlighting script for a certain Wiki
Syntax, now I want to check via autocommand if the edited text file is a
Wiki file:

    autocmd BufEnter *.txt call IsWikiSyntax()

The function looks like this:

    fun IsWikiSyntax()
      if match(getline(1,20),"^ \{0,1}\(=\{2,6}\)[^=]\+\1 *$") >= 0
        set textwidth=0
        set wrap
        set linebreak
        set filetype=wiki
      endif
    endfun

The pattern used in the match() call is the same as in the syntax highlighting
script. The idea is that the function looks for the occurance of the following
strings in the first 20 lines and activate change the filetype if it finds a
match. The searched strings could be of the type:

====== foo ======
===== foo =====
==== foo ====
=== foo ===
== foo ==

I am a bit confused because the above pattern works for the syntax highlighting
part but not for the  match() call. I tried several abbreviations of the above
pattern on a string via :echo match(line(1),"[pattern]") but always get "-1".

Does the match() function interpret patterns in a different way - or am my 
missing something else?

I am using Vim 7.0.174.

Thanks in Advance
Michael

-- 
Michael Klier

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