How to trim the value of a variable?

[Stuart Wright]

Hi folks, I have this code
Code:

<xf:if is="{$block.block_title} != 'Conclusion' && {$block.block_title} != 'Conclusion '">
and going by my coding background that the trim function removes leading and trailing spaces, I want to shorten it to
Code:

<xf:if is="<xf:trim>{$block.block_title}</xf:trim> != 'Conclusion'">
Except, that doesn't work, does it.
So how do I do this, please?
Thanks
How to trim the value of a variable?

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