<span tal:content="php:'This is some \' thing'"/>
<span tal:content="'This is some \' thing'"/>
<span tal:content="'This is some \' thing' | 'some thing'"/>
<span tal:content="nonexistantvariable | 'some \' thing'"/>
<span tal:content="'' | 'some \' thing' | string:else"/>
<span tal:content="string:This is some \' thing"/>